Make sure that there are no versions of SmartSound running. Press and hold the control-key while launching the SmartSound application. Keep the key down until you see the serial number window. SmartSound for Multimedia
users can run SmartSound, hold down cntrl and shift keys while selecting Preferences under the edit menu. You should see a tab called "Special". Click the tab and then click on the "repersonalize" button. Quit SmartSound and run it again as you normally would. It should then ask you for your serial number.